To search for secondary metabolites of Alnus hirsuta (Betulaceae), various chromatographic separations of the ethyl acetate soluble fraction of the stem bark of A. hirsuta led to the isolation of a new diarylheptanoid glycoside, (3 R )-1,7-bis-(4-dihydroxyphenyl)-3-heptanol 3- O -β- D -glucopyranosyl(1→3)-β- D -xylopyranoside (13) and twelve diarylheptanoid derivatives, namely, oregonin (1), rubranoside A (2), hirsutanonol 5- O -β- D -glucopyranoside (3), rubranoside B (4), rubranoside C (5), hirsutanonol (6), hirsutenone (7), (5 S )- O -methylhirsutanonol (8), platyphylloside (9), platyphyllonol 5- O -β- D -xylopyranoside (10), aceroside VII (11) and platyphyllenone (12). Isolates were assessed for their hepatoprotective effects against tert -butylhydroperoxide ( t -BHP)-induced toxicity in HepG2 cells. Of these isolates, compounds 1—8 showed significant hepatoprotective effects on t -BHP-induced damage to HepG2 cells, with 8 exhibiting the greatest protective effect (50.7±3.7% at a concentration of 10 μ M ).